For certain power distribution applications transmission of mechanical energy by hydraulic manipulation is preferable to other options for reasons of power density, arrangement flexibility, and controllability. At the present time, machines employed for the hydraulic transmission of mechanical energy primarily consist of hydraulic pumps and hydraulic motors employing reciprocating mechanical motion of pistons and valves to accomplish movement of pressurized working fluid. Due to reciprocation of primary function components the working fluid flow inherently involves the presence of pressure fluctuations and hence inherently feature the potential for propagation of undesirable noise and mechanical vibration. Hydraulic power systems featuring relatively high measures of working fluid pressure and relatively low measures of working fluid flow velocity are often identified as xe2x80x9chydrostaticxe2x80x9d power systems.
Over a number of years significant inventive effort has been directed toward the derivation of a xe2x80x9crotaryxe2x80x9d fluid displacement machine employing only rotationally dynamic mechanical components for working fluid manipulation. In comparison with reciprocating machines the rotary machine is perceived to offer advantages in terms of mechanical simplification and elimination of fluid flow pressure fluctuations. The radial vane type rotary machine has been the subject of particular attention in this regard.
Conceptually the rotary vane machine features a stationary hollow containment structure consisting of a containment cylinder with a precisely or approximately circular bore and with an end closure structure installed at each axial end. Said containment structure is fitted with ports for induction and discharge of working fluid through the structural boundary. A rotational armature approximately circular in cross-section and concentrically secured on a rotational shaft is installed within the bore of said containment cylinder. The diameter of said rotational armature is proportioned to create an annular cavity between the peripheral surface of said rotational armature and the bore of said containment cylinder. Said rotational shaft axially extends through the axial length of said containment structure and is radially constrained by rotational bearings. Axial ends of said rotational shaft are configured as necessary to interface with external rotational power systems. Said rotational shaft is aligned with its rotational axis parallel to but radially separated from the bore axis of said containment cylinder. Said rotational armature accommodates an axially aligned radial vane slot at each of several centers equally spaced around its periphery and said radial vane slot is proportioned to accommodate and provide sliding support for one radial vane. Said radial vane is axially proportioned to extend through the axial length of said rotational armature and radially proportioned to extend from within said radial vane slot to interface with the bore of said containment cylinder. Collectively the radial vanes subdivide said annular cavity into a number of annular segmental chambers. Since the rotational axis of said rotational shaft is radially separated from the bore axis of said containment cylinder the volume of each annular segmental chamber is dependent upon its rotational position and is cyclically manipulated upon rotation of said rotational armature. The cyclical relationship between annular segmental chamber volume and rotation of said rotational armature equates to the cyclical relationship between contained volume and piston movement featured in reciprocating type fluid displacement machines.
A number of patents have been awarded for rotary vane hydraulic power machine concepts however as of this writing none of the concepts presented in prior art are known to have matured sufficiently to demonstrate adequacy regarding one or more practical functional viability parameters. Functional viability of energy transmission machines is measured by their capability to meet thresholds for efficiency and power density within constraints imposed by natural physical phenomena.
The efficiency and power density of hydraulic rotational power machines are directly influenced by machine capabilities defined in terms of volume cycle efficiency, pressure cycle efficiency, mechanical efficiency, working fluid pressure amplification, and rotational velocity.
For rotary vane type machines volume cycle efficiency is directly related to the proportional relationship between the internal bore diameter of the containment structure and the diameter of the internal rotational armature. Pressure cycle efficiency is directly influenced by both the number of segmental chambers surrounding said rotational armature and the distance separating the rotational axis of said rotational armature from the bore axis of said containment structure. Pressure cycle efficiency is inversely influenced the relative thickness of the radial vanes and by hydrodynamic impedance imposed on the movement of working fluid as required to accomplish the cyclical manipulation.
Analysis demonstrates that the threshold for adequate pressure cycle efficiency is attained only when the number of segmental chambers surrounding said rotational armature exceeds a certain minimum value. However the radial vanes are, collectively, a potentially significant cause of degradation in mechanical efficiency due to frictional resistance at sliding interfaces. Additionally the radial vanes are, collectively, a potentially significant cause of degradation in mechanical efficiency if ancillary pumping of working fluid is incurred by reciprocating motion of the radial vane within the radial vane slot. For these reasons functional viability is dependent upon derivation the optimum balance between several efficiency considerations.
In addition to the efficiency considerations discussed above, power density is directly influenced the magnitude of working fluid pressure amplification, and the magnitude of rotational velocity. However hydraulic machines function by manipulation of an essentially non-compressible working fluid and so entail the possible occurrence of noise, vibration, and efficiency degradation due to high-pressure hydrodynamic impacting and low-pressure hydrodynamic cavitation. For these reasons acceptable limits for working fluid pressure amplification and rotational velocity and technical approaches for avoidance of hydrodynamic impacting and hydrodynamic cavitation phenomena are also functional viability considerations.
The principal features of several rotary vane type hydraulic machines presented in prior patent disclosures are reviewed below.
U.K. Pat. No. 114,584, U.K. Pat. No. 577,569, and Japan Pat. No. 63-9685 each discloses a rotary vane pump device featuring a stationary housing with an end closure structure installed at each axial end and with fluid transfer ports. Within said stationary housing a rotor is concentrically secured to a rotational shaft. Said rotational shaft is radially and axially constrained by rotational bearings installed in said end closure structure. Said rotor is fitted with an axially aligned radial vane slot at each of several centers uniformly distributed around its periphery. Each said rotor slot annularly constrains one radial vane but permits relative sliding motion in a radial direction. Said radial vane is radially constrained at each axial end by a rotating ring configured as an axially extended peripheral flange on a rotating disk. Said rotating ring is proportioned to maintain a constant distance between the outer peripheral edge of said radial vane and the bore of said stationary housing. Centripetal load induced by said radial vane due to rotor rotation is imposed on the said rotating ring by direct edge contact of said radial vane. Said rotating disk is radially and axially constrained by a low friction rotational bearing. The rotational axis of said rotating disk is aligned to be concentric with the longitudinal axis of the bore of said stationary housing. Said rotating disk maintains contact with the axial end of each said radial vane and with the axial end of said rotating armature.
All disclosures identified above present the primary mechanical features required for manipulation of hydraulic fluids and substantially focus on technical approaches toward minimization of friction particularly as related to radial vanes. However all disclosures identified above are essentially silent regarding other mechanical considerations inherently related to the functional viability of rotary vane hydraulic power devices.
This disclosure presents a rotary vane device for hydraulic transmission of rotational mechanical energy on a scale commonly associated with modern hydraulic power systems in industrial and marine service. Primary manipulation of the working fluid is accomplished without the use of reciprocating pistons, valves, or similar mechanical components and the device may function as either a hydraulic pump or hydraulic motor depending only upon the relative direction of flow of the working fluid.
The device primarily consists of a stationary structure for system containment, an internal rotational assembly for energy conversion, and volume compensating valves for protection from excessive pressure fluctuations. Said stationary structure primarily features a containment cylinder with a circular bore installed with diametrically opposed working fluid induction ports and working fluid discharge ports distributed along its axial length and with an end closure structure mechanically secured at each axial end. Said rotational assembly primarily features a rotational shaft, a rotational armature, a set of radial vanes, and one freely rotating radial vane constraint ring installed at each axial end of said armature. Said rotational shaft extends through the axial length of said stationary structure and is simply supported and radially constrained by a low-friction rotational bearing installed in each end closure structure. Said rotational shaft is aligned to rotate on an axis parallel to but radially separate from the bore axis of said containment cylinder. Said rotational shaft is configured to interface with an external rotational power generator or rotational power transmission device. Said rotational armature is concentrically installed on said rotational shaft within said containment cylinder. Said rotational armature features a circular cross-section and is configured as a hollow structural annulus fitted with a structurally integral disk at each axial end. Said rotational armature is diametrically proportioned with an outer diameter of approximately ninety percent of the effective bore of said containment cylinder. A radial vane slot axially proportioned to extend through the axial length of said rotational armature is installed at each of twelve centers uniformly distributed around the periphery of said rotational armature. Said radial vane slot is radially proportioned to extend through the thickness of said structural annulus to preclude efficiency degradation due to radial vane pumping. Said radial vane slot accommodates and annularly constrains one radial vane between linear bearing inserts. Said radial vane is proportioned to extend through the axial length of said rotational armature, radially extend through said structural annulus to approach the bore of said containment cylinder, and permit relative sliding motion within said radial vane slot. A radial vane edge-seal proportioned to make resilient sealing contact with the bore of said containment cylinder is installed on the radially outermost axial edge of said radial vane. A sliding block is installed at each axial end of said radial vane. Said radial vane constraint ring is diametrically proportioned to make a close but sliding fit with the bore of said containment cylinder and is axially and radially constrained by low-friction rotational bearings. Said radial vane constraint ring features an axially extended flange on its outer periphery with said axially extended flange diametrically and axially proportioned to radially constrain said sliding block installed on said radial vane. Said radial vane constraint ring accommodates a concentrically installed axial wear ring and a concentrically installed axial compression spring. Said axial compression spring is proportioned to constrain said axial wear ring to maintain resilient pressure contact with the axial end of said rotating armature. Axially aligned ports with non-return valves installed in the axial face of said wear ring permit high-pressure working fluid to augment the actuation force of said axial compression spring. A high-pressure volume compensation valve and a low-pressure volume compensation valve are installed in said containment cylinder and aligned to preclude the occurrence of hydraulic impacting hydraulic cavitation respectively.